down fire box?

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=115775
Printed Date: May 13, 2025 at 5:16 AM

Topic: down fire box?

Posted By: asquarecan
Subject: down fire box?
Date Posted: August 19, 2009 at 11:17 PM

Hey guys,

I am getting ready to build a box and I think I am going to build a down firing vented box and I was curious is there a certain distance I should be the box off the ground? From what I have seen in the past they are about 2" off the ground. Is that a good height?

I use my trunk a lot between snowboarding and throwing stuff in and around my trunk so I really dont want to take a chance having my sub get damaged and even with a grill I would be paranoid.

Any help would be greatly appreciated!

Thanks
Keith

Replies:

Posted By: boogeyman
Date Posted: August 20, 2009 at 9:30 AM

the sub should be 1/4 the size of the sub off the floor.................10 inch sub---2.5 inches......12 inch sub---3.0 inches

Posted By: aznboi3644
Date Posted: August 20, 2009 at 1:26 PM

never heard of that "rule" in my life.

I used to have a downfiring enclosure calculator...got it off the web somewhere...try searching

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Posted By: boogeyman
Date Posted: August 20, 2009 at 3:02 PM

I heard this "rule" over at DIY mobile audio.

Posted By: DYohn
Date Posted: August 20, 2009 at 3:59 PM

That particular "rule of thumb" may create the proper space, but the real answer is the exit area between the enclosure and the floor should be at least equal to the driver's Sd (the "exit area" is the total square inches of the opening you create when you place the subwoofer on the ground, including all four openings if it is unobstructed on all four sides.) It really is not about how far the speaker is from the ground, it is about how much air can move away from the enclosure.

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Posted By: asquarecan
Date Posted: August 20, 2009 at 6:07 PM

Thanks guys!

I will use this info while building my box!

Keith